The invention relates to four-wheel drive systems, including but not limited to a method for performing neutral tow braking on a four-wheel-drive vehicle.
Known four-wheel-drive powertrains of a four-wheel drive vehicle have an internal combustion engine and a multiple-ratio, geared transmission. The crankshaft of the engine is connected to torque input gearing of the transmission and the output shaft of the transmission is connected to a rear drive shaft, which delivers torque to a rear differential and to rear traction wheels for the vehicle.
A transfer case provides a torque flow path to the front wheels of the four-wheel drive vehicle. The transfer case normally operates in a four-wheel, high speed mode, a four-wheel, low speed mode and a neutral mode. The neutral mode, also known as a xe2x80x9cneutral towxe2x80x9d feature, allows four-wheel drive vehicles to be towed behind another vehicle, for example, a motor home, over long distances. The basic function of this feature is to shift the transfer case motor to a neutral position during towing, preventing transfer case damage during towing.
There are disadvantages with. known neutral tow methods. For example, one disadvantage occurs when the neutral tow feature is activated and the vehicle is unhooked on an inclined surface. When this occurs, the vehicle could roll away uncontrolled to possibly cause personal injury or property damage. Another disadvantage occurs in that the transfer case could be destroyed if the transfer case is engaged when the four-wheel drive vehicle is being towed, even if the vehicle""s transmission is in neutral.
Accordingly, there is a need for an improved neutral tow method that reduces the risk of injury to persons and property, and, overall, is more reliable.